Loudspeaker

Abstract

A coaxial loudspeaker has a first driver producing sound within a first frequency band and a second driver coaxial with the first driver producing sound within a second higher frequency band. The first driver includes a first moveable membrane coupled and moveable relative to a frame to generate sound waves within the first frequency band. The first moveable membrane extends from adjacent a central axis to an outer part above and spaced apart from a rim of the frame, the outer part being resiliently coupled to the rim. The second driver includes a second moveable membrane generating sound waves within the second frequency band. The second moveable membrane is behind or below the first moveable membrane and the resilient coupling is behind the first moveable membrane extending from the rim to the outer part so the surround is not an obstacle to second driver sound waves.

1 . A coaxial loudspeaker comprising:
 a first driver for producing sound within a first frequency band;   a second driver mounted coaxially with the first driver for producing sound within a second frequency band that includes frequencies that are higher than said first frequency band; and   a frame;   wherein the first driver comprises a first moveable membrane coupled to the frame and arranged to move relative to the frame to generate sound waves within said first frequency band in response to input drive signals, the first moveable membrane extending from an inner part adjacent a central axis of the loudspeaker to an outer part located above and spaced apart from a rim of the frame, the outer part of the first moveable membrane being coupled to the rim of the frame by a resilient surround;   wherein the second driver comprises a second moveable membrane arranged to move to generate sound waves within said second frequency band in response to input drive signals,   wherein the second driver is supported by the first driver such that the second moveable membrane is located behind the first moveable membrane; and   wherein the resilient surround sits behind the first moveable membrane extending from the rim of the frame to the outer part of the first moveable membrane so that the surround does not present an obstacle to sound waves generated by the second driver.   
     
     
         2 . A coaxial loudspeaker according to  claim 1 , wherein the second driver comprises a horn to guide the sound waves generated by the second driver towards a space in front of the first moveable membrane, and wherein the profile of the horn matches a profile of the first moveable membrane. 
     
     
         3 . A coaxial loudspeaker according to  claim 1 , wherein the resilient surround extends from a first edge thereof that is fixed to the rim of the frame to a second edge thereof that is fixed to the outer part of the first moveable membrane. 
     
     
         4 . A coaxial loudspeaker according to  claim 1 , wherein the resilient surround comprises one or more rolls that extend between the rim of the frame and the outer part of the first moveable membrane. 
     
     
         5 . A coaxial loudspeaker according to  claim 1 , wherein the resilient surround extends in a direction that is inclined outwardly away from the central axis from the rim of the frame to the outer part of the first moveable membrane. 
     
     
         6 . A coaxial loudspeaker according to  claim 1 , wherein the resilient surround extends in a direction that is substantially parallel to the central axis of the loudspeaker. 
     
     
         7 . A coaxial loudspeaker according to  claim 1 , wherein the resilient surround further comprises one or more air permeable walls that extend between the rim of the frame and the outer part of the first moveable membrane. 
     
     
         8 . A coaxial loudspeaker according to  claim 1 , further comprising a motor assembly that is coupled to the frame and to the first moveable membrane such that in response to said input drive signals, the motor assembly causes the first moveable membrane to move relative to said frame. 
     
     
         9 . A coaxial loudspeaker according to  claim 1 , wherein the first moveable membrane has a circular, elliptical or oval shaped outer part. 
     
     
         10 . A coaxial loudspeaker according to  claim 1 , wherein the first frequency band lies within a frequency range below 3000 Hz and wherein the second frequency band lies within a frequency range above 2000 Hz. 
     
     
         11 . A coaxial loudspeaker according to  claim 1 , wherein the surround has an annular shape about said central axis and comprises a wall that extends in a direction that is substantially parallel with the central axis or that extends in an outward direction extending away from the central axis. 
     
     
         12 . A method of making a coaxial loudspeaker comprising:
 providing a first driver for producing sound within a first frequency band;   providing a second driver for producing sound within a second frequency band that includes frequencies that are higher than said first frequency band;   providing a frame;   coupling a first moveable membrane of the first driver to the frame so that the first moveable membrane can move relative to the frame to generate sound waves within said first frequency band in response to input drive signals,   arranging the first moveable membrane to extend from an inner part adjacent a central axis of the loudspeaker to an outer part located above and spaced apart from a rim of the frame,   mounting the second driver on the first driver so that the second driver is coaxial with the first driver and so that a second moveable membrane of the second driver is behind the first moveable membrane of the first driver;   coupling the outer part of the first moveable membrane to the rim of the frame by a resilient surround so that the resilient surround sits behind the first moveable membrane and does not present an obstacle to sound waves generated by the second driver.